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I just got my dad's old Aurex Toshiba SB-A45 amp that he said was somewhat of a flagship amp at the time he bought it. I like the overall sound of it, high resolution and very musical, but with a somewhat floppy and uncontrolled bass. It looks great, and the fact that it has voltage led lights makes it more interesting.
Anyway, to the point. Every time the source feeding it gets close to -0db this terrible crackling noise appears, and the balance from left to right is shifted. The problem is the same for the headphone out and the speaker out, so it's not due to a bad connection. On some bassy tracks or tracks with high transient response, the symptom is unbearable. Lowering the bass gain solves the problem, and raising it makes it worse.
I have never built any DIY amps, so my knowledge is limited.
Do someone recognise this problem and know any easy way to solve it? I was thinking this might be due to a broken capacitor?
__________________ Headphones: Ultimate Ears UE-11 x2 (fantastic!), Grado SR325i Experiences: GS-1000, HD 600+650, AKG K701, Super.fi 5 Pro & EB
Future Plans: iMod, Lisa III, Portable V-cap dock
__________________ Headphones: Ultimate Ears UE-11 x2 (fantastic!), Grado SR325i Experiences: GS-1000, HD 600+650, AKG K701, Super.fi 5 Pro & EB
Future Plans: iMod, Lisa III, Portable V-cap dock
I would start cheap, and do things that shoudl generally be done for older equiptment anyway.
Start by cleaning all of the pots (volume, bass, treble, etc). It could be as simple as some low-level noise from one of these controls that doesn't become apparent until you reach higher levels.
Also, make a close examination of the bottom of the circuit board looking for cracked/cold solder joints. Retouching with some fresh solder and flux should fix them up. Another thing to look for is cracked/burned resistors that may have died over time. Don't forget to look at the signal level meter and protection circuitry, as they are both connected to the outputs and can cause problems.
If you get lucky, this will do it for you.
Next would be to replace the old, and probably dried-out electrolytic caps, starting with the two big power supply caps. Use the same value (uF) and equal or greater voltage rating. Entirely possible that will do it as well.
Out of curiosity, what are the output devices (large transistors on the heatsink)?
__________________
There is a very fine line between "hobby" and "mental illness."
Last edited by BrianDonegan; 05-07-2008 at 10:44 PM.
Problem with my old amp
Linear Mode
